Wet Digestion
Definition
Viscera is digested with HNO3 + H2SO4 + HClO4 (or HNO3 + H2O2) at controlled temperature. Closed-vessel microwave-assisted digestion in Teflon bombs preserves volatile metals (Hg, As, Se) and is now standard at DFSS and CFSL toxicology divisions.
- Primary acids
- Nitric acid, sulfuric acid, perchloric acid (or hydrogen peroxide as substitute)
- Sample type
- Viscera (organ tissue)
- Modern standard method
- Closed-vessel microwave-assisted digestion in Teflon containers
- Metals preserved by microwave method
- Mercury, arsenic, selenium
Common questions
What acids are used in wet digestion for metallic poisons?+
Wet digestion typically uses nitric acid (HNO3) alone or combined with sulfuric acid (H2SO4) and perchloric acid (HClO4). Some methods substitute perchloric acid with hydrogen peroxide (H2O2). These strong oxidizing agents break down tissue samples on a hot plate.
Why is microwave-assisted digestion preferred in toxicology labs?+
Closed-vessel microwave digestion in Teflon bombs is now standard because it preserves volatile metals like mercury, arsenic, and selenium that might otherwise be lost during heating.
What sample material is digested in metallic poison analysis?+
Viscera (internal organs) from the suspected poisoning victim are digested using the chemical and heat process. This breaks down the tissue so toxicologists can isolate and measure trace metals in the body.
Related terms
- Dry Ashing
- Viscera or hair is dried and incinerated in a muffle furnace at 450 to 550 degrees Celsius. Inorganic ash is dissolved in...
- Acid Blank
- A parallel digestion of reagents in an empty vessel, subtracted from the sample to correct for trace metal contamination in the acids.
- Arsenic (As)
- Metalloid; trivalent arsenite (As III) is 60 times more toxic than pentavalent arsenate (As V). Thiol-group blocker that poisons mitochondrial enzymes (pyruvate...
- Ashing Aid
- A salt (typically magnesium nitrate) added before dry ashing to fix volatile elements as less volatile salts that survive the furnace.
- Hydride Generation (HG-AAS)
- Sensitivity booster for As, Sb and Se. Sample plus NaBH4 in acid liberates AsH3 / SbH3 / SeH2 gas, which is swept...
- Lead (Pb)
- Cumulative neurotoxin from chronic occupational exposure (battery recycling, smelter work), leaded paint, contaminated cosmetics (low-grade sindoor, surma, kohl), and adulterated Ayurvedic preparations....
- Marsh Test (1836)
- Confirmatory test for arsenic devised by James Marsh after the Bodle case (1832), in which Marsh was unable to convince a jury...
- Matrix Destruction
- Breakdown of organic tissue into water, CO2 and mineral residue so bound metals are released as free ions. Without it, AAS reads...
- Mercury (Hg)
- Three toxic forms: elemental (vapour from broken thermometers, dental amalgam), inorganic salts (mercuric chloride, corrosive sublimate), and organic (methylmercury from biomagnification, ethylmercury...
- Microwave-Assisted Digestion
- Closed-vessel digestion in PTFE or quartz bombs at 1200 to 1800 W, reaching 200 degrees Celsius and 1500 psi in 30 to...
- Reinsch Test
- Classical screen for arsenic, antimony, mercury and bismuth. A clean copper strip is immersed in the acidified sample (concentrated HCl, near-boiling) for...
- Thallium (Tl)
- The 'poisoner's poison' because thallium sulphate is tasteless, odourless and colourless. Substitutes for potassium in cellular transport. Alopecia at 2 to 3...
Explained in these topics
- Dry Ashing and Wet Digestion for Metallic PoisonsChemical oxidation on a hot plate with concentrated mineral acids: nitric alone or with sulphuric and perchloric.
- Metallic Poisons: Arsenic, Mercury, Lead and ThalliumViscera is digested with HNO3 + H2SO4 + HClO4 (or HNO3 + H2O2) at controlled temperature. Closed-vessel microwave-assisted digestion in Teflon bombs preserves...